Messier 5

Acquisition:

Bortle 7 skies
Nikon D7000 camera
Orion Apex 102mm telescope, 1300mm focal length
iOptron CEM26 mount
30s x 143 frames
f/12.7
ISO 400

Processing:

Siril:

Background extraction
Background neutralization + color calibration
Generalized hyperbolic transformation

RawTherapee:

Black point
L*a*b chrominance/luminance adjustment
Luminance noise reduction
3x3 median filter

GIMP:

Luminance curve adjustment
Saturation
Color balance
Touch of noise reduction